Dual Cure Cyanate Ester Inkjet Composition

Abstract

The present invention relates to an inkjet composition having 1.0-5.0 mol/kg acryloyl groups comprising: i) photo polymerization reactive compound (M) containing exactly one acryloyl group, ii) photo polymerization reactive compound (N) containing at least two acryloyl groups, iii) radical photoinitiator (R), iv) cyanate ester compound (D) containing at least two cyanate groups and v) cyanate ester curing catalyst (C), wherein (M) is different from (D) and (N) is different from (D),

25-50 mol % of the contained acryloyl groups are provided by the reactive compound (N) and the molar ratio of contained acryloyl groups to contained cyanate groups of compound (D) is 0.30 to 0.95.

Claims

1. An inkjet composition comprising: i) photo polymerization reactive compound (M) containing exactly one acryloyl group, ii) photo polymerization reactive compound (N) containing at least two acryloyl groups, iii) radical photoinitiator (R), iv) cyanate ester compound (D) containing at least two cyanate groups, and v) cyanate ester curing catalyst (C), wherein (M) is different from (D) with the proviso that cyanate ester compound containing exactly one acryloyl group and additionally containing at least two cyanate groups is subsumed to (D), (N) is different from (D) with the proviso that cyanate ester compound containing at least two acryloyl groups and additionally containing at least two cyanate groups is subsumed to (D), 25-50 mol % of the contained acryloyl groups are provided by the reactive compound (N) and the molar ratio of contained acryloyl groups to contained cyanate groups of compound (D) is 0.30 to 0.95, and the inkjet composition has 1.0-5.0 mol/kg acryloyl groups.

2. The inkjet composition according to claim 1, having 1.7-3.5 mol/kg acryloyl groups.

3. The inkjet composition according to claim 1, wherein 30-45 mol % of the contained acryloyl groups are provided by the reactive compound (N).

4. The inkjet composition according to claim 1, wherein 80-100 mol % of the reactive compound (N) are species containing not more than three acryloyl groups.

5. The inkjet composition according to claim 1, wherein the molar ratio of contained acryloyl groups to contained cyanate groups of compound (D) is 0.36 to 0.94.

6. The inkjet composition according to claim 1 wherein at least 30 wt. % of the species of (D) 4,4′-ethylidenediphenyl dicyanate.

7. The inkjet composition according to claim 1, wherein the radical photoinitiator (R) comprises a phosphinoxide-based photoinitiator.

8. The inkjet composition according to claim 1 wherein the cyanate ester curing catalyst (C) comprises an aluminum metal catalyst.

9. The inkjet composition according to claim 1 wherein 90-100 wt. %, of the contained ingredients are species of (M), (N), (R), (D) and (C).

10. The inkjet composition according to claim 1, having a viscosity of 10-40 mPa s at 45° C., where the viscosity is measured on a thermally controlled rotational rheometer in cone-plate geometry, cone diameter: 60 mm, zero-gap distance: 0,061 mm, cone angle: 0,5°, shear-rate 600s−1, at temperatures from 40 to 60° C. with a heating ramp of 2 K/min following the DIN EN ISO 3219.

11. The inkjet composition according to claim 1 which does not contain cationic or anionic (photo)polymerization initiator.

12. The inkjet composition according to claim 1 which contains less than 6 wt. % radical polymerizable monomers not containing acryloyl groups.

13. The inkjet composition according to claim 1, additionally containing one or more of a stabilizer, a wetting agent, a defoamer, a radical polymerization inhibitor, and a pigment.

14. A process for printing a three-dimensional object comprising the steps of: (a) jetting an inkjet composition by means of a printing machine to form a layer in a configured pattern corresponding to the shape of the object, the inkjet composition comprising: i) photo polymerization reactive compound (M) containing exactly one acryloyl group, ii) photo polymerization reactive compound (N) containing at least two acryloyl groups, iii) radical photoinitiator (R), iv) cyanate ester compound (D) containing at least two cyanate groups, and v) cyanate ester curing catalyst (C), wherein (M) is different from (D) with the proviso that cyanate ester compound containing exactly one acryloyl group and additionally containing at least two cyanate groups is subsumed to (D), (N) is different from (D) with the proviso that cyanate ester compound containing at least two acryloyl groups and additionally containing at least two cyanate groups is subsumed to (D), 25-50 mol % of the contained acryloyl groups are provided by the reactive compound (N) and the molar ratio of contained acryloyl groups to contained cyanate groups of compound (D) is 0.30 to 0.95, and the inkjet composition has 1.0-5.0 mol/kg acryloyl groups, (b) irradiating the formed layer to form a photo-cured layer, (c) sequentially repeating steps (a) and (b) to form a plurality of photo-cured layers in order to prepare a green body of the three-dimensional object, and (d) heating the green body to post cure the three-dimensional object.

15. The process according to claim 14, further comprising printing and curing a support ink to stabilize the green body, and removing the cured support ink after step c) and before the performance of step (d) by treating with an aqueous washing liquid, wherein the cured support ink is water soluble.

16. The process according to one claim 14 wherein the heating step (d) is performed in such a way that temperatures between 110 and 140° C. are kept at least for 5 hours.

17. The process according to claim 16, wherein in the heating step (d) the relevant increase of the temperature is limited to 2 K/min.

18. The process according to claim 14, wherein in step (b) the irradiation is performed by means of an UV lamp and the exposure time of each ink layer is 0.1-2 s.

19. A three-dimensional object manufactured according to the process according to claim 14.

20. A three-dimensional object manufactured from an inkjet composition comprising: i) photo polymerization reactive compound (M) containing exactly one acryloyl group, ii) photo polymerization reactive compound (N) containing at least two acryloyl groups, iii) radical photoinitiator (R), iv) cyanate ester compound (D) containing at least two cyanate groups, and v) cyanate ester curing catalyst (C), wherein (M) is different from (D) with the proviso that cyanate ester compound containing exactly one acryloyl group and additionally containing at least two cyanate groups is subsumed to (D), (N) is different from (D) with the proviso that cyanate ester compound containing at least two acryloyl groups and additionally containing at least two cyanate groups is subsumed to (D), 25-50 mol % of the contained acryloyl groups are provided by the reactive compound (N) and the molar ratio of contained acryloyl groups to contained cyanate groups of compound (D) is 0.30 to 0.9, and the inkjet composition has 1.0-5.0 mol/kg acryloyl groups.

21. The inkjet composition according to claim 1, wherein 90-100 mol % of the reactive compound (N) are species containing not more than three acryloyl groups.

22. The inkjet composition according to claim 1, wherein at least 60 wt.-% of the species of (D) are 4,4′-ethylidenediphenyl dicyanate.

23. The inkjet composition according to claim 1, wherein the radical photoinitiator (R) comprises diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide and/or phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide.

24. The inkjet composition according to claim 1, wherein the cyanate ester curing catalyst (C) comprises aluminum acetylacetonate.

25. The inkjet composition according to claim 1, wherein 97-100 wt. % of the contained ingredients are species of (M), (N), (R), (D) and (C).

26. The inkjet composition according to claim 1, which contains less than 2 wt. % radical polymerizable monomers not containing acryloyl groups.

Description

EXAMPLE 1

[0112] Isobornlyacrylate (IBOA) (25.0 wt %), acryloyl morpholine (ACMO) (12.5 wt %), trimethylpropane triacrylate (TMPTA) (12.5 wt %), butylhydroxytoluol (BHT) (0.3 wt %), Omnirad 819 (1.0 wt %), Genorad 16 (0.5 wt %), BYK 333 (0.2 wt %), AroCy 10 L US (48.2 wt %) (bisphenol-E based cyanate ester with two cyanate groups) and additional 500 ppm Al(acac).sub.3 were mixed and filtered over 1 μm.

TABLE-US-00001 Mol of curing % of all Wt % functionality UV- % of all in (for curing curing Example 1 formu- 1 kg final function- function- Compound lation formulation) alities alities IBOA 25 1.20 36% 17% ACMO 12.5 0.88 26% 13% TMPTA 12.5 1.26 38% 18% AroCy 10 L 48.2 3.64 52%

[0113] The ink was inkjet UV printed and post-cured from RT to 220° C. with a heating ramp of 1K/min.

[0114] The final properties of the final object were:

[0115] Tensile strength: 75 MPa

[0116] Elongation at break: 2.5%

[0117] E-Modulus: 3200 MPa

[0118] Green body measurement after UV-curing (40×7×4 mm) A

[0119] Green body measurement after thermal-curing (40×7×4 mm): A

[0120] The said inkjet composition comprises: [0121] I) mol/kg acryloyl groups of (M) and (N): 3.35 [0122] II) mol % of acryloyl groups provided by reactive compound (N): 37.8 [0123] Ill) molar ratio of contained acryloyl groups (M) and (N) to contained cyanate ester groups of compound (D): 0.92

Example 2

[0124] Isobornlyacrylate (12.5 wt %), acryloyl morpholine (7.5%), trimethylolpropane triacrylate (7.5%), BHT (0.3 wt %), Omnirad 819 (1 wt %), Genorad 16 (0.5 wt %), BYK 333 (0.2 wt %), AroCy 10 L US (68.2 wt %) as bisphenol-E based cyanate ester and additional 1500 ppm Al(acac).sub.3 were mixed and filtered over 1 μm.

TABLE-US-00002 Wt % Mol of % of all UV- % of all in functionality curing curing Example 2 formu- (for 1 kg final function- function- Compound lation formulation) alities alities IBOA 12.5 0.60 32%  8.5% ACMO 7.5 0.53 28%  7.5% TMPTA 7.5 0.75 40% 10.8% AroCy 10 L 68.2 5.16 73.2%

[0125] The ink was inkjet UV printed and post-cured from RT to 220° C. with a heating ramp of 1 K/min.

[0126] The final properties of the final object were:

[0127] Tensile strength: 80 MPa

[0128] Elongation at break: 2.7%

[0129] E-Modulus: 2900 MPa

[0130] HDT B: 196° C.

[0131] Green body measurement after UV-curing (40×7×4 mm) B

[0132] Green body measurement after thermal-curing (40×7×4 mm): B

[0133] The viscosity stability of Example 2 is measured to be as following:

TABLE-US-00003 Time [days] Viscosity at 60° C. Formulation at 60° C. [mPa .Math. s] Example 2 0 9 7 15

[0134] The said inkjet composition comprises: [0135] I) mol/kg acryloyl groups of (M) and (N): 1.89 [0136] II) mol % of acryloyl groups provided by reactive compound (N): 40.2 [0137] III) molar ratio of contained acryloyl groups (M) and (N) to contained cyanate ester groups of compound (D): 0.37

Example 3

[0138] For AroCy 10 L US as the thermally reacting component the viscosity was measured after storage at 60° C. at different time intervals in the presence of different catalysts and concentrations (see table below).

TABLE-US-00004 Formulation 1 2 3 4 Catalyst Al(acac).sub.3 Co(acac).sub.3 Time of ppm storage at 700 1500 700 1500 60° C. Viscosity [mPa .Math. s] at 60° C. [days] after storage at 60° C. 0 12.3 13.8 14.0 13.9 2 15.7 17.9 14.6 17.8 5 20.8 25.4 20.1 67.4 7 24.7 32.4 32.0 429 Viscosity 201 235 229 3086 Increase in %

[0139] The viscosity increase in the presence of the cobalt-catalyst is more pronounced than for the aluminum catalyst.

Example 4

[0140] Isobornlyacrylate (20.8 wt %), acryloyl morpholine (10.3 wt %), trimethylolpropane triacrylate (10.3 wt %), CN 981 (6.32 wt %), Omnirad 819 (1.0 wt %), Genorad 16 (0.25 wt %), BYK 333 (0.2 wt %) AroCy 10 L US (51.0 wt %) and Aluminium acetylacetonate (0.03 wt %) were mixed and filtered over 1 μm.

TABLE-US-00005 Wt % Mol of % of all % of all in functionality UV-curing curing Example 4 formu- (for 1 kg final function- function- Compound lation formulation) alities alities IBOA 20.8 1.00 35% 15% ACMO 10.3 0.73 26% 11% TMPTA 10.3 1.04 37% 16% CN 981 6.32 0.07  3%  1% AroCy 10 L 51.0 3.86 58%

[0141] The ink was inkjet UV printed and post-cured as follows: 30-130° C. at 1 K/min, 130° C./10h, 130-150° C. at 1 K/min, 150° C./2h, 150-180° C. at 1 K/min, 180° C./2h, 180-200° C. at 1 K/min, 200° C./2h, 200-220° C. at 1 K/min, 220° C./10 min, 220-° C. at −5 K/min.

[0142] The final properties of the final object were:

[0143] Tensile strength: 86 MPa,

[0144] Elongation at break: 3.9%,

[0145] E-Modulus: 3500 MPa.

[0146] HDT B: 141° C.

[0147] Green body measurement after UV-curing (40×7×4 mm) A

[0148] Green body measurement after thermal-curing (40×7×4 mm): A

[0149] The said inkjet composition comprises: [0150] I) mol/kg acryloyl groups of (M) and (N): 2.85 [0151] II) mol % of acryloyl groups provided by reactive compound (N): 39.3 [0152] III) molar ratio of contained acryloyl groups (M) and (N) to contained cyanate ester groups of compound (D): 0.74

Example 5

[0153] Isobornlyacrylate (17.1 wt %), acryloyl morpholine (7.8 wt %), trimethylolpropane triacrylate (7.3 wt %), CN 981 (6.3 wt %), Omnirad 819 (0.5 wt %), Genorad 16 (0.25 wt %), BYK 333 (0.2 wt %) AroCy 10 L US (60.0 wt %) and Aluminium acetylacetonate (0.03 wt %) were mixed and filtered over 1 μm.

TABLE-US-00006 Wt % Mol of % of all % of all in functionality UV-curing curing Example 5 formu- (for 1 kg final function- function- Compound lation formulation) alities alities IBOA 17.1 0.82 38% 12% ACMO 7.8 0.55 25%  8% TMPTA 7.3 0.74 34% 11% CN 981 6.3 0.07  3%  1% AroCy 10 L 60.0 4.54 67%

[0154] The ink was inkjet UV printed and post-cured as follows: 30-130° C. at 1 K/min, 130° C./10h, 130-150° C. at 1 K/min, 150° C./2h, 150-180° C. at 1 K/min, 180° C./2h, 180-200° C. at 1 K/min, 200° C./2h, 200-220° C. at 1 K/min, 220° C./10 min, 220-° C. at −5 K/min.

[0155] The final properties of the final object were:

[0156] Tensile strength: 86 MPa,

[0157] Elongation at break: 4.2%,

[0158] E-Modulus: 3400 MPa.

[0159] HDT B: 194° C.

[0160] Green body measurement after UV-curing (40×7×4 mm) A

[0161] Green body measurement after thermal-curing (40×7×4 mm): A The said inkjet composition comprises: [0162] I) mol/kg acryloyl groups of (M) and (N): 2.19 [0163] II) mol % of acryloyl groups provided by reactive compound (N): 37.2 [0164] III) molar ratio of contained acryloyl groups (M) and (N) to contained cyanate ester groups of compound (D): 0.48

Example 6

[0165] Isobornlyacrylate (20.7 wt %), trimethylolpropane triacrylate (6.7 wt %), CN 981 (4.4 wt %), Omnirad 819 (2.3 wt %), Genorad 16 (0.29 wt %), BYK 333 (0.2 wt %) AroCy 10 L US (65.4 wt %) and Aluminium acetylacetonate (0.033 wt %) were mixed and filtered over 1 μm.

TABLE-US-00007 Wt % Mol of % of all % of all in functionality UV-curing curing Example 6 formu- (for 1 kg final function- function- Compound lation formulation) alities alities IBOA 20.7 1.00 58% 15% TMPTA 6.7 0.68 39% 10% CN 981 4.4 0.05  3%  1% AroCy 10 L 65.4 4.94 74%

[0166] The ink was inkjet UV printed and post-cured as follows: 30-130° C. at 1 K/min, 130° C./10h, 130-150° C. at 1 K/min, 150° C./2h, 150-180° C. at 1 K/min, 180° C./2h, 180-200° C. at 1 K/min, 200° C./2h, 200-220° C. at 1 K/min, 220° C./10 min, 220-° C. at −5 K/min.

[0167] The final properties of the final object were:

[0168] Tensile strength: 86 MPa

[0169] Elongation at break: 3.5%

[0170] E-Modulus: 3400 MPa

[0171] HDT B: 189° C.

[0172] HDT A: 124° C.

[0173] Flexural Strength: 111 MPa

[0174] Flexural Modulus: 2800 MPa

[0175] Izod unnotched: 264 J/m

[0176] The said inkjet composition comprises: [0177] I) mol/kg acryloyl groups of (M) and (N): 1.72 [0178] II) mol % of acryloyl groups provided by reactive compound (N): 42.5 [0179] Ill) molar ratio of contained acryloyl groups (M) and (N) to contained cyanate ester groups of compound (D): 0.35

Example 7-11

[0180] To screen ink and material properties of potential inkjet formulations molded specimens are cured for 30 s from each side in translucent silicon molds from the bottom at a distance of 15 cm by UV-light (LED 395 nm, 16 W/cm 2). Then a thermal post-curing is carried out. Testing results of this photopolymerized and oven-cured bulk specimens are then emphasizing in a good proximity the final material performance of material jetted and post-cured formulations, even though the preparation process in the first curing-step of the interpenetrating system differs.

[0181] Example 7-11 illustrate a varying formulation ratio in a way that the degree of functional acrylate groups by (N) are within the limits of claimed dual-curing inkjet inks or beyond the bounds to highlight the correlation of printing application and material characteristics.

[0182] Isobornylacrylate, acryloyl morpholine, trimethylpropane triacrylate, Omnirad 819, Genorad 16, AroCy 10 L US and Al(acac).sub.3 were mixed in ratios as shown in Table 1.

[0183] The ink was molded as described above and post-cured as follows: 30-130° C. at 1 K/min, 130° C./10h, 130-150° C. at 1 K/min, 150° C./2h, 150-180° C. at 1 K/min, 180° C./2h, 180-200° C. at 1 K/min, 200° C./2h, 200-220° C. at 1 K/min, 220° C./10 min, 220-30° C. at −5 K/min.

[0184] As shown in Table 1 the ink and material properties vary with increasing network density due to the increase of mol % by (N). Thus, the green body strength with labelling C is too low and the material in green state too soft, whereas a warpage of category D is too high and the material has too much internal tension to print and post-cure complex three dimensional objects in a sufficient dimensional accuracy with regard to the digital file. Additionally, good final mechanical properties in terms of toughness and flexibility, of preferably 70-100 MPa tensile strength and preferably 3-5% elongation at break are only achieved by balancing out the degree of functional acrylate groups by (N).

TABLE-US-00008 TABLE 1 Compound (in Example Example wt % in formulation) 7 8 IBOA 18.8 16.8 ACMO 7.2 7.2 TMPTA 3.5 5.5 AroCy L 10 US 70.0 70.0 Omnirad819 0.3 0.3 Genorad16 0.25 0.25 Al(acac).sub.3 0.035 0.035 I) mol/kg acryloyl groups 1.76 1.87 II) mol % of acryloyl 20.1 29.8 groups by (N) III) molar ratio 0.33 0.35 Results Viscosity at 50° C. [mPa .Math. s] 12 13 Viscosity at 50° C. [mPa .Math. s] 24 27 after 8 d at 60° C. Shore-Hardness after A11 A28 UV-cure Shore-Hardness after D81 D84 thermal-cure Green body strength B A after UV-cure (40 mm × 7 mm × 2 mm) Green body strength after C B thermal-cure (40 mm × 7 mm × 2 mm) Warpage after thermal-cure B C Tensile strength [MPa] 44 73 Elongation at beak [%] 1.7 3.3 E-Modulus [MPa] 3100 2900 HDT B [° C.] 215 213 T.sub.g [° C.] 146, 245 162, 243 Network density [mol/m.sup.3] 1900 1900 Compound (in Example Example Example wt % in formulation) 9 10 11 IBOA 14.4 11.7 8.6 ACMO 7.2 7.2 7.2 TMPTA 7.9 10.6 13.7 AroCy L 10 US 70.0 70.0 70.0 Omnirad819 0.3 0.3 0.3 Genorad16 0.25 0.25 0.25 Al(acac).sub.3 0.035 0.035 0.035 I) mol/kg acryloyl groups 2.00 2.14 2.31 II) mol % of acryloyl 40.0 50.1 60.1 groups by (N) III) molar ratio 0.38 0.40 0.44 Results Viscosity at 50° C. [mPa .Math. s] 14 14 16 Viscosity at 50° C. [mPa .Math. s] 29 33 37 after 8 d at 60° C. Shore-Hardness after A53 A69 A78 UV-cure Shore-Hardness after D85 D86 D86 thermal-cure Green body strength A A A after UV-cure (40 mm × 7 mm × 2 mm) Green body strength after A A A thermal-cure (40 mm × 7 mm × 2 mm) Warpage after thermal-cure C C D Tensile strength [MPa] 78 81 65 Elongation at beak [%] 3.6 3.4 2.7 E-Modulus [MPa] 3000 3100 2800 HDT B [° C.] 208 221 219 Tg [° C.] 182, 242 246 243 Network density [mol/m.sup.3] 2000 2500 3600